I was missing The Bolt-Caster, Raze-Lighter, Tlaloc, Fabian Strategy, and the ever elusive Telesto (I missed xur that weekend he sold it whenever it was). Anyway grinded out all those during the last couple weeks since you have to wait for arms day. And just kept running challenge mode, eye of the gate lord, the ultra knight in the dreadnaught etc. Just this morning I ran a challenge of elders and Syloc dropped a special engram and I just thought like oh boy it's going to be Hereafter or Plan C for the millionth time and after I was done there I just decided all my engrams as fast as possible and saw my Grimore card at the bottom while the game was still deciding all my other engrams and boom! TELESTO. TL;DR I got all the exotic weapons. You probably don't care. I'm a pretty happy dude though!